The Niangua darter Etheostoma nianguae is a threatened stream fish endemic to the Osage River basin of Missouri's Ozark uplands. We studied the darter's reproductive behavior under natural conditions in the wild to assist recovery efforts. In addition, techniques for captive propagation were developed in the event that wild populations should suffer precipitous declines. Seven spawning events were witnessed by snorkelers in swift riffle areas at mean (± SD) water depths of 23 ± 5 cm, column current velocities of 83 ± 12 cm/s and focal current velocities of 43 ± 9 cm/s. This combination of depth and velocity was used only for spawning; darters were found at slower velocities and greater depths when not spawning during spring and at slower velocities during summer. Niangua darters in captivity spawned in 38 liter aquaria with fine uniform substrate and no current velocity, and larvae were reared to the juvenile stage. Time from fertilization to hatching was 10–11 d at 16 C. Larvae swam up 3 d after hatching and remained in the water column 31–33 d before returning to the substrate. We suggest a spawning protocol that includes capturing wild males and females during April, isolating spawning pairs in 38 liter aquaria with fine substrate and maintaining low light levels during hatching. Young can be reared on brine shrimp nauplii, zooplankton and, later, frozen adult brine shrimp. A chronology of Niangua darter reproductive and early life history events is provided.
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Vol. 149 • No. 2